1. Field of the Invention
The present invention is related to a riding pavement saw which is capable of performing a variety of pavement sawing tasks with a single machine.
2. Description of the Prior Art
Devices for sawing pavement are well known and riding pavement saws are now being introduced. Pavement sawing is done to establish expansion joints, to improve roads and to increase the life of roadways. Pavement develop cracks for a number of reasons including freeze thaw cycles, shifting subgrades and excessive loads as with trucking. Once cracks develop, water and dirt fill the space and the rate of deterioration for the pavement increases rapidly. To prevent further cracking, the crack is sawed out to form a smooth channel and is then cleaned, dried and filled with joint sealant materials which expand and contract with the roadway without the materials breaking their bond so that foreign materials such as water are not allowed to leak through and weaken the subgrade.
Joints which are filled are of two general types, straight line cuts and random cracks. Straight line cuts are generally found on concrete slabs on roadways and for creating rumble strips. The type of blade used for sawing straight lines varies with the type of pavement being sawed, but generally 14" and larger diameter blades are used in straight line sawing applications.
A second type of straight line sawing is performed for patching. In patching, a section of pavement is sawed around its circumference and then removed. To ease removal, the outline is sawed at an angle rather than vertically, so that the section of pavement can be slid out without the sides of the section and surrounding pavement interfering, easing removal. This sawing has the blades typically angled at 2.degree.-3.degree. from vertical.
Random cracks require sharp turns to follow the cracks which wind in an arbitrary, irregular pattern. Smaller diameter blades, typically 8 to 10 inches, are used for random crack sawing so there is less blade in the pavement which improves maneuverability and reduces drag or friction. The saw operator must have a clear unobstructed view of the crack in order to steer the saw so that the crack is followed closely to ensure a smooth channel surface for filling and sealing. Heretofore, random cracks and cracks on curves have been sawed with manual saws wherein the operator pushes or pulls and steers the saw from the rear. Manual steering and propulsion of a push type saw is physically demanding on the operator, making operation a difficult and tiring job. A self-propelled riding saw greatly reduces the physical requirements needed for sawing cracks, especially when the saw must be turned. The driver in a riding saw needs to have the blade in full view preferably almost straight down. In addition, the blades should be between the front wheels for support, as shown in U.S. Pat. No. 3,663,060, with the blades as close to the center of turning as possible so that the blades do not face sideways resistance when turning. If the blades are not substantially centered on the turning radius, the blades clear too wide of a path through turns as the blades are dragged through the turns.
In addition to sawing random cracks and straight line sawing, other sawing operations are performed including sawing recesses for placing reflectors in highways at spaced intervals. The depressions which are sawed usually have a special cross section which requires accurate timing for raising and lowering of the blades to form the correct shape. Some reflectors require sloping entering the depression and exiting the depression while other depressions require a slope entering the depression but a relatively steep exit slope. To achieve the proper entrance and exit slopes for reflector depressions, the timing of lifting and lowering the saw blades is critical.
Heretofore, riding saws were not capable of performing multiple sawing tasks such as sawing straight line joints, sawing random or curve cracks, and sawing depressions for reflectors. Different jobs requires different blades and a different steering or seating position. It has not been possible to alter the steering and drive mechanisms on a single riding saw to accommodate the various saw blades and steering positions required to perform more than one sawing operation. Prior Art riding saws use a belt drive system for driving the saw blades. Moving the cutting head to multiple positions or multiple angles is very difficult since the engine itself must be relocated or angled for proper belt alignment. Drive belts make adjustments for different applications cumbersome and time consuming.
It can be seen then, that the requirements for sawing straight line joints, random cracks and special sawing operations are difficult to meet with a single sawing machine. The present inventions provides a single machine capable of performing a number of different sawing operations.